A top drive well drilling apparatus typically includes a top drive system (TDS) connectable to the upper end of a drill string to drive the drill string rotatively and which moves upwardly and downwardly with the string during the drilling operation. The TDS includes a tubular main shaft, the lower end of which is threadedly connectable to the upper end of the drill string and through which drilling mud is delivered downwardly to the string and drill bit from a gooseneck and swivel assembly at the upper end of the unit. The unit further includes a motor to drive the main shaft rotatively as the well is drilled. A washpipe assembly comprising at least one dynamic seal and a tubular element is threadedly connected between the top of the main shaft and the bottom of the gooseneck/swivel assembly.
The washpipe assembly is located above the rotating TDS main shaft and below the stationary gooseneck. Drilling mud is pumped at high pressure through the gooseneck and washpipe assembly and into the main shaft. The dynamic seals of the washpipe assembly act as the main sealing elements between the connection of the washpipe assembly to each of the TDS main shaft and the gooseneck. During drilling operations these dynamic seals experience extreme wear and require frequent replacement.
Replacement of the dynamic seals requires an operator to disengage the connection of the washpipe assembly with each of the main shaft and the swivel/gooseneck, to remove the washpipe assembly and to install a replacement washpipe assembly. Installation and removal of the washpipe assembly are each accomplished in a similar manner. In conventional systems, both operations typically involve manually striking a nut that threadedly connects the washpipe assembly to the main shaft and manually striking a nut that threadedly connects the washpipe assembly to the swivel/gooseneck assembly. The manually striking is typically accomplished by a sledgehammer, thereby imparting an impact torque to either engage or disengage the nuts. Repeated application of such impact torque may be necessary, particularly when the connection must be disengaged after extended exposure to the extreme stresses and environmental conditions of the drilling environment. In the best of circumstances, this operation is unsafe and time-consuming. Moreover, because the torque applied is uncontrolled, i.e. not measured, a determination of whether the nuts of the washpipe assembly are fully engaged or disengaged is left to the judgment of the operator that is installing or removing the washpipe assembly. Thus, increasing the likelihood of operator error and subsequent damage to the rig.
Accordingly, a need exists for a new apparatus and method for installing a washpipe assembly in a safe and controlled manner.